Although the HIV-1 epidemic in India is mainly due to subtype C, other subtypes have also been reported from different parts of India. HIV-1 LTR sequence analysis from six HIV-1 infected individuals from North India was carried out to determine the nature and extent of variations. Four out of six samples formed a unique phylogenetic cluster which was close to subtype B. The other two samples (A3 and S3) turned out to be novel mosaic recombinants showing resemblance to subtypes B, B/C-India and B/C-Myanmar gene segments. All four subtype B LTR samples and the two B/C recombinants showed conserved as well as unique polymorphisms in all of the putative transcription factor binding sites (TFBS). These changes may potentially alter basal as well as Tat-mediated HIV-1 LTR promoter activation. The two recombinants possessed three copies of the NF-κB TFBS as seen with the majority of subtype C and recombinant B/C isolates reported earlier, but the other four non-recombinant B-LTRs showed only two copies of the NF-κB site. This is the first study to show a dominance of unique subtype B-LTRs and strongly suggests that this region could also be a hot spot for the formation of highly complex inter subtype B/C recombinants.
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